Anyone who has used a cellular telephone or another type of wireless device is familiar with the occasional xe2x80x9chiccupsxe2x80x9d which occur in the reception of voice, data or video information. Many of these are due to a loss of signal, others are due to increased bit error rates (abbreviated xe2x80x9cBERxe2x80x9d), which results in reduced voice quality or lower data throughputs. Generally, a wireless communication signal is transmitted to and from a moving object, such as a wireless device, to a fixed transceiver or the like through space. This space is known as the xe2x80x9cchannelxe2x80x9d through which the signal travels. One important measurement when it comes to the transmission of digital information through a channel is the BER of the channel. A channel which has a high BER is undesirable.
There exists a number of ways to minimize the BER of a channel. One way is to improve the way that a received signal is processed in order to extract original data embedded within an original, transmitted signal. That is, instead of changing the channel itself (which is many times impractical to do), the method used to generate the received signal from the transmitted signal may be improved. Many methods for generating a received signal from a transmitted signal rely on information related to the speed of the moving object and the amount of noise in the channel. For example, the object""s speed is related to a characteristic called xe2x80x9cchannel fadingxe2x80x9d. Some methods for generating a received signal involve estimating the affects of channel fading. It has been recognized that the BER of a channel can be reduced or minimized if a transceiver within a wireless device is provided with information about channel fading. In other words, if a transceiver is supplied with information which describes how errors were introduced into the signal by channel fading, then the transceiver can be adapted to correct these errors.
Because the speed of an object and the amount of noise in the channel affects a signal traveling through the channel it becomes important to estimate these affects. To date, there has been no easy way to estimate the speed of a wireless device or the noise in the channel from a received version of the signal.
Such estimates, if reliable, could be used to reduce the BER of a signal and thus improve the performance of wireless devices.
Accordingly, it is desirable to provide for methods and devices for improving the performance of wireless devices.
It is also desirable to provide for methods and devices for improving the performance of wireless devices using information about an object""s speed and the amount of noise present in a transmission channel.
Other objectives, features and advantages of the present invention will become apparent to those skilled in the art from the following description taken in conjunction with the accompanying drawings.
In accordance with the present invention there are provided methods and devices for improving the performance of a wireless device. As envisioned by the present inventor the present invention comprises methods and devices for generating a SPEED metric from a mean value of a differential signal and generating a NOISE metric from a variance value of the differential signal. One or both metrics may be generated in this manner provided the number of symbols used to generate the mean and variance values is a limited number of symbols.
Two examples of devices envisioned by the present invention are an arithmetic logic unit (xe2x80x9cALUxe2x80x9d) and a wireless device comprising an ALU.
In the novel methods and devices, the SPEED metric comprises a value which is: the square of the absolute value of the magnitude of the mean value of the differential signal; or the magnitude of the mean value of a differential signal; or the square root of the magnitude of the mean value of a differential signal.
The NOISE metric comprises the variance of the differential signal which is shown to be approximately equal to twice the variance of the noise in a received baseband signal while at the same time being independent of the speed at which an object, such as a wireless device, moves.
As envisioned by the present inventor, the novel methods and devices can be adapted to generate an optimum Least Mean Square (xe2x80x9cLMSxe2x80x9d) step size for use in channel estimates which bears a substantially linear relationship to a logarithm of a ratio of a SPEED metric to a NOISE metric.
The present invention and its advantages can be best understood with reference to the drawings, detailed description of the preferred embodiments and claims that follow.